We propose to examine the role of G protein coupled receptors (GPCRs) in two related physiological events - secretion and cellular senescence. The secretion of important molecules such as hormones and cytokines are regulated by GPCRs but the mechanistic basis of this regulation is not clear. We have discovered that G protein 23 complexes translocate to the Golgi on GPCR activation and induce secretory vesicle formation in the trans-Golgi. Extracellular signals can thus regulate secretion through 23 translocation. Our first aim is to test whether 23 translocation plays a role in GPCR regulation of cathepsin D secretion from a lung carcinoma cell and insulin from a pancreatic beta cell. We have found that secretion of cathepsin D, a protease that promotes tumor growth and metastasis, is regulated by a bradykinin receptor. Insulin secretion is also known to be regulated by GPCRs, including the M3 muscarinic receptor. The second aim is to examine the potential role of receptor induced G protein 23 complex translocation in cellular senescence. The third aim is to uncover mechanisms at the basis of GPCR regulation of senescence. Cellular senescence is a process by which stressed cells stop dividing but remain viable. It is thought to play contradictory roles - protecting the cell from cancerous growth but promoting proliferation of surrounding pre-neoplastic cells through enhanced secretion of various molecules. We propose to pursue these aims based on recent results that a translocation proficient G protein 3 subunit induces senescence. The role of GPCRs in cellular senescence is not clearly understood although they are the major sensors of extracellular cues. Identifying the molecular mechanisms at the basis of GPCR regulation of secretion and senescence will provide novel targets for the design of therapeutic interventions that can have an impact on cancer, diabetes and the deleterious effects of ageing.